Pool cleaning system

ABSTRACT

A method for charging a pool cleaning robot, the method may include positioning a first wireless charging element of a pool cleaning robot within a charging range of a second wireless charging element of a floating unit; wherein the floating unit is electrically and mechanically coupled to an external power source, wherein the positioning comprises moving at least one of the pool cleaning robot and the floating unit; and wirelessly charging, by the second wireless charging element, the first wireless charging element, wherein the charging occurs while maintaining the first wireless charging element within the charging range of the floating unit, despite movements of the floating unit.

CROSS REFERENCE

This application claims priority from U.S. provisional patent 62/643,764filing date Mar. 16, 2018.

BACKGROUND

Pool cleaning robots are adapted for use for cleaning a pool while beingconnected to electrical power cables or to a hose of a suction system.The hose and/or power cable can get tangled and may temporarily limitthe usage of the pool.

There is a growing need to provide efficient charging systems andmethods for charging pool cleaning robots.

SUMMARY OF THE INVENTION

There may be provided a pool cleaning system that may include a floatinginductive charger whereby the pool cleaning robot can autonomously andautomatically attach itself to the said charger in order to charge itson-board batteries and disengage from the said charger to continuecleaning the pool. A more detailed description is given below.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to understand the invention and to see how it may be carriedout in practice, an embodiment will now be described, by way of anon-limiting example only, with reference to the accompanying drawings,in which:

FIG. 1 is an example of a pool and of a pool cleaning system;

FIG. 2 is an example of a pool, a floating unit, and a pool cleaningrobot of the pool cleaning system at different positions;

FIG. 3 is an example of a pool, a floating unit, and a pool cleaningrobot of the pool cleaning system at different positions;

FIG. 4 is an example of a user, a pool, a floating unit, and a poolcleaning robot of the pool cleaning system;

FIG. 5 is an example of a cradle;

FIG. 6 is an example of a floating unit, and a pool cleaning robot ofthe pool cleaning system;

FIG. 7 is an example of a pool, a floating unit, and a pool cleaningrobot of the pool cleaning system;

FIG. 8 is an example of a pool, a floating unit, and a pool cleaningrobot of the pool cleaning system;

FIG. 9 is an example of a pool, a floating unit, and a pool cleaningrobot of the pool cleaning system;

FIG. 10 is an example of a pool, a floating unit, and a pool cleaningrobot of the pool cleaning system;

FIG. 11 is an example of a pool, a floating unit, and a pool cleaningrobot of the pool cleaning system;

FIG. 12 is an example of a floating unit, and a pool cleaning robot ofthe pool cleaning system;

FIG. 13 is an example of a floating unit, and a pool cleaning robot ofthe pool cleaning system;

FIG. 14 is an example of a floating unit that has an anemometer; and

FIG. 15 is an example of a method.

DETAILED DESCRIPTION OF EMBODIMENTS

“Swimming pool” or “pool” mean any spa or tank or any reservoircontaining liquid.

Because the apparatus implementing the present invention is, for themost part, composed of optical components and circuits known to thoseskilled in the art, circuit details will not be explained in any greaterextent than that considered necessary as illustrated above, for theunderstanding and appreciation of the underlying concepts of the presentinvention and in order not to obfuscate or distract from the teachingsof the present invention.

In the following specification, the invention will be described withreference to specific examples of embodiments of the invention. It will,however, be evident that various modifications and changes may be madetherein without departing from the broader spirit and scope of theinvention as set forth in the appended claims.

The word “comprising” does not exclude the presence of other elements orsteps then those listed in a claim. It is understood that the terms soused are interchangeable under appropriate circumstances such that theembodiments of the invention described herein are, for example, capableof operation in other orientations than those illustrated or otherwisedescribed herein.

There may be provided a floating unit that may include an inductivecharger that may include a contactless charging unit that is arranged tocharge a pool cleaning robot in a contactless manner. In order toprovide enough power to the pool cleaning robot (and enable the poolcleaning robot to clean the pool for relatively long cleaning periods)the floating unit should receive power via a cable. The floating unitmay be implemented in existing pools, and does not require to retrofitthe pool to include a fixed wireless charging unit. Furthermore—thelocation of the external power source and the location of the floatingunit can be determined by the user, and may be changed upon userrequest—thereby allowing adjustments and eases the installation of thesystem.

The charging is contactless in the sense that the contactless chargingunit (or a contactless charging element of said unit) of the floatingunit and a contactless charged unit (or a contactless charging element)of the pool cleaning robot do not need to contact each other during thecharging process.

Thus—the pool cleaning robot may or may not contact the floating unitduring the charging process.

The contactless charged unit of the pool cleaning robot may bepositioned anywhere in the pool cleaning robot—but it may be positionedproximate to an inner part of a housing (or cover or enclosure) of thepool cleaning robot. FIG. 2 illustrates a coil 223 of a contactlesscharged unit that is located at the top (below the housing) of the poolcleaning robot.

FIG. 3 illustrates a coil 322 of a contactless charged unit that islocated at the front (behind the housing) of the pool cleaning robot.

Charging by using a floating unit (a) does not require to installcontactless charging units within the walls of the pool—thus it may beused in existing pools, (b) is cheaper than installing contactlesscharging units in existing pools and in new pools, (c) may replace along power cord that is constantly connected to the pool cleaning robot,(d) may enable to easily determine (and/or change) the location of thefloating inductive charger, and (f) provides a safe method (contactless)for charging the pool cleaning robot.

The pool cleaning robot may navigate towards the floating unit using aknown (or predefined or estimated) location of the floating unit, and byusing one of more sensors such as image sensors, sonar, radar,electromagnetic sensors, and the like. The pool cleaning robot mayautonomously move towards the unit and/or may move under the control (atleast partially) of an external device or user.

The floating unit may include one or more transmitters for transmittinghoming beacons and/or information about the location of the floatinginductive charger.

The floating unit may remain substantially static (pending to windand/or pool water condition) when the pool cleaning robot progressestowards the floating unit.

It is assumed in this specification that the floating unit may notremain fully static or immobile as it is not attached to any solid poolstructure, such a wall or a portion of a wall, a ladder, a ledge and thelike.

The floating unit may move freely towards, away and sideways from thepool cleaning robot whereby, the nature of the movements are rollingfrom side-to side, pitching and forward or backwards sideways driftingin relation to the pool cleaning robot.

The floating unit may sense the spatial relationship between thefloating unit and the pool cleaning robot (using one or more sensors ofany type) and may inform the pool cleaning robot or yet anothercomputerized system about the spatial relationship.

The pool cleaning robot may sense the spatial relationship between thethe pool cleaning robot (using one or more sensors of any type) and thefloating unit and may adjust its approach trajectory according to theconstantly changing spatial relationship.

It is a major objective of this specification for the pool cleaningrobot to travel in the swimming pool to connect with the internalcharging surface of the charging float in one single motion or‘in-one-go’, without the necessity to perform another or a secondarycorrective trajectory to connect with the said float.

Nevertheless, the trajectory program to connect with the charging floatinherently includes a reconnect trajectory procedure for the event of alast moment failure or a perceived, pre-calculated failure to complete alinear, single motion docking procedure with the charging float. In sucha case, the pool cleaning robot may want to avoid a miss or anuncontrolled collision that will divert the charging float off location(albeit at very low speeds and impacts) requiring to perform aregenerated trajectory approach to connect to the charging float.

The pool cleaning robot may be configured to monitor the movement of thefloating unit (for example while cleaning the pool when moving in thepool without cleaning the pool) and to determine a parameter related toa movement of the floating unit. The parameter may include the amount ofmovements, the repetitiveness of the movement, the angular deviations(tilt) and/or any other parameter that may provide an indicationregarding a chances of succeeding to perform the charging of the poolcleaning robot.

For example—strong wind may cause the floating unit to move dramaticallyfrom tile angle to the other any may reduce the chances of successfullymaintaining (or even forming) the small distance between the wirelesscharging elements of the floating unit and the pool cleaning robottogether.

Thus the pool cleaning robot may delay the charging process when itdetermines that these chances are below a threshold (for example—below30, 40, 50, 60 or 70%) and even reduce its battery power consumption(stop the cleaning, clean more slowly or otherwise reduce its powerconsumption) till there are better chances of succeeding to power thepool cleaning robot.

The same evaluation may be executed during the approach towards thefloating unit—the pool cleaning robot may determine to stop the approachand wait (for example at least 5, 10, 15, 20, 25, 30, 35 minutes andeven more) till the water is calmer (or otherwise the chances of successare better).

The floating unit and/or the pool cleaning robot may determine to stop acharging process if either decides that the chances of completing thecharging process are lower than a threshold.

The frequency and/or duration of the charging periods may be determinedbased on the movements of the floating unit and/or the turbulence—forexample it may be easier to maintain the small distance (within thecharging range) between the pool cleaning robot and the floating unitfor longer periods when the water is calmer. The pool cleaning robot maydetermine, even when its battery is relatively full (and may still powerthe pool cleaning robot to perform some cleaning operation—for examplemay still clean the pool for more than 5, 10 or 20 minutes) decide toinitiate a charging operation—when the water is relatively calm and/orthe floating unit is relatively stable.

It should be noted that the floating unit itself may determine its ownmovement parameter and either determine whether charging is possibleand/or may send the parameter to the pool cleaning robot (or to a thirdentity such as a computer) that may determine whether the performing acharging attempt/what is the duration and timing of the chargingattempt.

Additionally, or alternatively, the floating unit may instruct the poolcleaning robot how to move based on the sensed spatial relationship.

The floating unit may include additional components or may belong to afloating unit that includes additional components. These additionalcomponents may include, for example, any sensors for sensing and/oranalyzing the water of the pool, illumination means, a chemical materialdispenser, communication means, a propulsion unit for moving thefloating unit, and the like.

For example—the floating unit may include (in addition to thecontactless charging unit) at least one out of

-   (a) a chemical material dispenser-   (b) a Biological or chemical water analysis module-   (c) a pool anti drowning or unauthorized entry alarm (camera,    acoustic, pressure)-   (d) a floating battery-   (e) a surface motorized skimmer-   (f) or float for a variety of applications.

The pool cleaning robot can be charged while being submerged or semisubmerged in the pool water.

The pool cleaning system may include one or more of the followingelements:

-   -   a. a pool cleaning robot that may include        -   i. an electromagnetic induction coil 222        -   ii. hollow housing that has a front section side, rear, left            side, right side, upper and lower sides. 510        -   iii. a filtering unit 501        -   iv. a moveable or detachable cover or lid that may be opened            to remove the filter. 511        -   v. an inlet for allowing un-filtered fluid to enter the            housing and be filtered by the filtering unit; 512        -   vi. an outlet for allowing filtered fluid to exit the pool            cleaning robot; 513        -   vii. a propulsion mechanism. It may include, for example            jets and/or at least one drive motor 502        -   viii. one or more sensor for sensing the vicinity of the            pool cleaning robot; 503        -   ix. a controller for controlling the operation and            navigation of the pool cleaning robot. 504        -   x. A rechargeable battery 505 fed by the a electromagnetic            induction coil.        -   xi. A communication module 506 for communicating with the            floating unit and/or another entity.        -   xii. A processor (such as but not limited to an image            processor) 507 for receiving sensed information (such as            images), determining the location of the floating unit            and/or determining the spatial relationship and/or            estimating or determining the future location of the            floating unit and/or determining a path of the pool cleaning            robot towards the floating unit given the current movements            of the floating unit.    -   b. a power supply that may be external to the pool and may be        electrically coupled (for example tethered) to the floating unit    -   c. a floating electric cable.    -   d. a caddy or carriage adapted to carry the cleaner, power        supply and the floating charger.    -   e. at least one on board rechargeable battery    -   f. a floating unit that may include (each one of the following        may be included within a housing of the floating unit, outside        the housing, and the like):        -   i. a contactless charging unit that may include an            electromagnetic induction coil system        -   ii. a transducer of any other communication unit for            communicating with the pool cleaning robot.        -   iii. electromagnetic sensors around the charging coils            surface        -   iv. wireless communications means to communicate with smart            computer devices, the internet, a Bluetooth® device,    -   a Wi-Fi® or a Li-Fi device.

The floating device may communicate its own status wirelessly or act asan intermediary for the submerged or semi submerged pool cleaning robot.

Communications between Pool cleaning robot and/or float with the enduser may be performed by means of a dedicated remote control

The electromagnetic sensors of the pool cleaning robot and of thefloating unit may be used for aligning the the pool cleaning robot andof the floating unit during an attachment procedure and to also keepboth attached during the charging process and to disengage when chargingends.

A top cover or lid of the pool cleaning robot that may compriseinduction coils

Each one of the contactless charging unit and the contactless chargedunit may include, in addition to the coils, conductors that areelectrically coupled to the coils.

In the contactless charging unit, the coil may be connected to the powercord, to a power regulating circuit, to a rechargeable battery of thefloating unit.

In the contactless charged unit, the coil may be connected to a powerregulating circuit, to a rechargeable battery of the pool cleaningrobot.

A coil is merely an example of a contactless charging element.

A electronic control system control system comprising a PCB and memorycapacity that controls the entire operation of the pool cleaning systemand its sensors

The pool cleaning system may comprise such sensors as: camera(s),accelerometer, acoustic/sonar sensor, Li-Fi sensor, RPM sensors,infra-red sensor, laser sensor, GPS communications, gyroscope, compassand the like

The pool cleaning robot may have any other component that allows thepool cleaning robot to clean submerged parts of the pool. Forexample—the pool cleaning robot may include one or more brush wheels forscrubbing submerged parts of the pool, an intermediary brush (not shown)and the like.

There may be provided a autonomous battery powered pool cleaning systemthat comprises a floating unit that may float freely on the pool watersurface; whereby the said floating unit includes a contactless chargingunit that may be wired to an electrical power supply (for example—bymeans of a tethered cable); whereby the pool cleaning robot canautonomously and automatically navigates to and then travels verticallyto attach itself to the said floating unit in order to start chargingits on-board batteries; at charging end the pool cleaning robotdisengages from the said floating unit to continue cleaning the pool.

The said physical attachment to the said floating unit may be performedby the following steps:

-   -   a) pool cleaning robot batteries signals control that battery        pool is reduced and needs charging;    -   b) pool cleaning robot scans the environment to pinpoint float        location    -   c) travelling on the pool floor or on pool wall until vertically        underneath the floating unit or in the vicinity of the floating        unit.    -   d) if underneath, pool cleaning robot may apply downward        vertical water jet thrusts to rise up to water level and to        maneuver to the exact matching charging surface of the float        charger.    -   e) in the vicinity of the floating unit, such as in a        substantially vertical wall climbing position, the pool cleaning        robot will maneuver to the exact matching charging surface of        the float charger. The pool cleaning robot may be in a        substantially horizontal position to the water surface or to the        bottom of the pool.    -   f) in another embodiment, the coils may be located at one of the        ends of the pool cleaning robot so the attachment position would        be in an upright position.    -   g) In order to travel to an upright position that is vertical to        the water surface or to the bottom of the pool, rear and side        jets may utilized.    -   h) upon arriving to the vicinity of the float charger, whether        in a vertical or in a horizontal position, the electromagnetic        sensors signal and align the pool cleaning robot charging        surface with the float charger charging surface.    -   i) The pool cleaning robot remains attached to the float charger        for the duration of the charging and may disengage after        termination.    -   j) end user may retrieve and pull the float charger and the        robot out of the pool when required, disconnect the charger from        the power supply and neatly store the components on a dedicated        caddy or trolley.

FIG. 1 illustrates pool 10, pool cleaning robot 22, floating unit 24,power cable 26 and power source 28.

Pool 10 has bottom 11 and sidewalls (such as sidewalls 12 and 13). Thewaterline is denoted 14.

Pool cleaning robot 22 includes a coil 223 of a contactless charged unitand a sensor 224.

Floating unit 24 may include an antenna (for wireless communication)214, a coil 242 of a contactless charging unit (which is electricallycoupled to cable 26), and one or more sensors 243 and 244.

The pool cleaning robot 22 travels along a path 90 that leads it fromthe bottom of the pool towards the floating unit 24.

FIG. 2 illustrates the pool cleaning robot at different positioned—atthe bottom of the pool, climbing sidewall 12 and contacting the floatingunit (or at least being positioned in proximity to the floating unit14)—thereby allowing a contactless charging process of the pool cleaningrobot.

FIG. 2 illustrates a coil 222 of the contactless charged unit that ispositioned below the top 221 of the housing of the pool cleaning robot.

FIG. 2 also shows a coil 242 of a contactless charging unit of thefloating unit. During the contactless charging process coils 242 and 222do not touch each other but are close to each other (for example are upto 6 centimeters from each other).

FIG. 3 illustrates a coil 223 of the contactless charged unit that ispositioned near the front edge of the housing of the pool cleaningrobot.

During the contactless charging process coils 242 and 223 do not toucheach other but are close to each other (for example are up to 6centimeters from each other).

FIG. 4 illustrates a user 100 that has a mobile computerized device 110that may be used for controlling the floating unit and/or the poolcleaning robot.

FIG. 5 depicts a trolley or a caddy with space to carry and to store thepool cleaning robot, its power supply and the floating charger.

FIG. 6 illustrates the floating unit 24 as including a upper portion2411 and a lower portion 2419 that extends below the upper portion (thatmay float above the water)—and includes a second contactless chargingelement 242 (such as but not limited to a coil or any inductor), whilethe pool cleaning robot 22 includes a first contactless charging element222 (such as but not limited to a coil or any inductor) located at thetop of the pool cleaning robot—within or outside the housing of the poolcleaning robot.

FIG. 7 illustrates pool 10, waterline 1111, power cable 26, power source28, floating unit 24 that includes a upper portion 2411 and a lowerportion 2419 that extends below (at an one side) of the upper portion(that may float above the water)—and includes a second contactlesscharging element 242 (such as but not limited to a coil or anyinductor), while the pool cleaning robot 22 includes a first contactlesscharging element 222 (such as but not limited to a coil or any inductor)located at the top of the pool cleaning robot—within or outside thehousing of the pool cleaning robot.

FIG. 8 illustrates pool 10, waterline 1111, power cable 26, power source28, floating unit 24 that includes a upper portion 2411 and two lowerportions 2412 and 2413 that extend below (and near opposite sides of) ofthe upper portion (that may float above the water). Each of the twolower portions includes a second contactless charging element 242 (suchas but not limited to a coil or any inductor), while the pool cleaningrobot 22 includes a pair of first contactless charging elements 222(such as but not limited to a coil or any inductor) located at bothsides of the pool cleaning robot and the top of the pool cleaningrobot—within or outside the housing of the pool cleaning robot.

FIG. 9 differs from FIG. 8 by illustrating three first contactlesscharging elements 222 located at top of the pool cleaning robot, atupper parts of both sidewalls of the pool cleaning robot- and alsoillustrating three corresponding second contactless charging elements242 located at each one of upper portion 2411, and the two lowerportions 2412 and 2413.

FIG. 10 illustrates pool 10, waterline 1111, power cable 26, powersource 28, floating unit 24 that includes a upper portion 2411 and alower portion 2419 that extends below (at an one side) of the upperportion (that may float above the water)—and includes a secondcontactless charging element 242 (such as but not limited to a coil orany inductor), while the pool cleaning robot 22 includes a firstcontactless charging element 222 (such as but not limited to a coil orany inductor) located at the top of the pool cleaning robot—within oroutside the housing of the pool cleaning robot.

FIG. 10 differs from FIG. 7 by the spatial relationship between the poolcleaning robot 22 and the floating unit 24 and by the location of thesecond contactless charging element 242.

In FIG. 7 the second contactless charging element 242 was located at theinner end of lower portion 2419—and the pool cleaning robot waspositioned directly below the upper portion 2411 during the charging. InFIG. 10 the second contactless charging element 242 is located at theexternal end of lower portion 2419—and the pool cleaning robot was notpositioned directly below the upper portion 2411 during the charging—itis still submerged but is located at the side of the upper portion.

The pool cleaning robot may be magnetically coupled to the floating unitduring the charging process. The magnetically coupling may be executedby having one or more magnets within the pool cleaning robot and in thefloating unit—see FIG. 11 magnet 229 in the pool cleaning robot andmagnet 249 in the floating unit. The magnet may be located within (orattached) to only one of the pool cleaning robot and the floatingunit—and the other one (of the pool cleaning robot and the floatingunit) may include an element made of a magnetic material. The magnet maybe a permanent magnet or an electromagnet in which current is providedduring the charging period and may not be fed (or be substantiallyreduced) once the charging period ends.

The pool cleaning robot may be mechanically coupled to the floating unitduring the charging process. Any mechanical unit, device, or mechanismmay be used. The mechanically coupling may be performed by one or moreelement of the floating unit, by one or more element of the poolcleaning robot and the like. The mechanical coupling may be implementedby any locking and unlocking mechanism (denoted 302 in FIG. 12), by arigid or flexible attachment elements (denoted 301 in FIG. 12), by ahook 303 and opening 304 (FIG. 13), and the like. The locking andunlocking may include any number of elements, may be controlled by thefloating unit, may controlled by the pool cleaning robot, and the like.

FIG. 14 illustrates a floating unit that include an anemometer 120.

The anemometer 120 includes a housing 122 that may be hollow and have acylindrical interior (or other shaped interior) 122 that surrounds thefins 121 of the anemometer. The fins 121 may be rotated by the wind andturn around an axis 124. The axis may be mechanically coupled to thehousing 122 via support elements 123. The housing 122 may be supportedby support elements 125 such as legs.

The anemometer may indicate the rate and direction of drifting of thefloat if a wind at the water surface of the pool places strain on thefloat to deflect it from its location. Furthermore, the wind directionand its intensity may be used to forecast where the float may be headingto and where it may be located in order to assist with the plotting ofthe pool cleaning robot trajectory to connect with the charging float.

FIG. 15 illustrates method 400.

Method 400 may be for charging a pool cleaning robot.

Method may include steps 410, 420 and 430.

Step 410 may include positioning a first wireless charging element of apool cleaning robot within a charging range of a second wirelesscharging element of a floating unit. The floating unit may beelectrically and mechanically coupled via one or more coupling elementsto an external unit. The positioning may include moving at least one ofthe pool cleaning robot and the floating unit. The one or more couplingelements may include one or more cables, one or more wires, one or morenets, and the like.

The charging range may be limited to few millimeters (for examplebetween 0.1 and 9 millimeters). Other values of the charging range maybe provided—for example more than few millimeters.

The floating unit may move (for example by the wind and/or flows of thefluid within the pool), whereas the movement may be repetitive or not.The positioning may include estimating the future movements of thefloating unit (by the pool cleaning robot or the floating unit) andwherein the propagating takes into account the future movements (untilreaching the floating unit).

Step 420 may include wirelessly charging, by the second wirelesscharging element, the first wireless charging element. The chargingoccurs when the first wireless charging element may be within thecharging range of the floating unit.

Step 410 may include at least one of the following:

-   -   a. Detecting, during the positioning and by at least one of the        floating unit and the pool cleaning robot, a spatial        relationship between the pool cleaning robot and the floating        unit; and    -   b. Positioning the first and second charging elements within the        charging range in response to the spatial relationship.    -   c. Instructing the pool cleaning robot (by the floating unit or        another entity) to move based on the spatial relationship.    -   d. The moving the floating unit based on the spatial        relationship.    -   e. Moving the floating unit to a predefined area that may be        known to the pool cleaning robot.    -   f. Sensing by the floating unit an impact of a wind on the        floating unit.    -   g. Positioning the first and second charging elements within the        charging range in response to the impact of the wind.    -   h. Moving the pool cleaning robot below the floating unit.    -   i. Rotating the pool cleaning robot or performing any        propagating path by the pool cleaning robot.    -   j. Attaching the pool cleaning robot to the floating unit during        a wireless charging period.    -   k. Mechanically coupling the pool cleaning robot to the floating        unit, at least during the wireless charging.    -   l. Magnetically coupling the pool cleaning robot to the floating        unit, at least during the wireless charging.    -   m. Calculating a meeting point between the pool cleaning robot        and the floating unit.    -   n. Based on the meeting point determine whether to progress (for        example move the pool cleaning robot) along a current path        towards the floating unit.    -   o. Based on the meeting point determining whether to change        current path—redirecting a progress towards the floating unit.    -   p. The redirection may be required when the current progress        path will lead the pool cleaning robot to reach the floating        unit at a position that increases an instability of the floating        unit docking. For example—meeting the floating unit away from        the center of the floating unit.    -   q. Calculating a future position and orientation of the floating        unit due to floating unit movements selected out of rolling,        pitching and sideways drifting, and directing the pool cleaning        robot towards the future position.    -   r. delaying a charging of the pool cleaning robot when movements        of the floating unit exceed a threshold.

Step 430 may include moving the pool cleaning robot away from thefloating unit—after ending the charging.

Any combination of a subject matter of any claim may be provided. Forexample, for each set of claims that includes a single independent claimand multiple dependent claims—each dependent claim may depend on anyother dependent claim.

Furthermore, the terms “a” or “an,” as used herein, are defined as oneor more than one. Also, the use of introductory phrases such as “atleast one” and “one or more” in the claims should not be construed toimply that the introduction of another claim element by the indefinitearticles “a” or “an” limits any particular claim containing suchintroduced claim element to inventions containing only one such element,even when the same claim includes the introductory phrases “one or more”or “at least one” and indefinite articles such as “a” or “an.” The sameholds true for the use of definite articles. Unless stated otherwise,terms such as “first” and “second” are used to arbitrarily distinguishbetween the elements such terms describe.

Thus, these terms are not necessarily intended to indicate temporal orother prioritization of such elements. The mere fact that certainmeasures are recited in mutually different claims does not indicate thata combination of these measures cannot be used to advantage.

We claim:
 1. A method for charging a pool cleaning robot, the methodcomprises the steps of: positioning a first wireless charging element ofa pool cleaning robot within a charging range of a second wirelesscharging element of a floating unit; wherein the floating unit iselectrically and mechanically coupled to an external power source,wherein the positioning comprises moving at least one of the poolcleaning robot and the floating unit; and wirelessly charging, by thesecond wireless charging element, the first wireless charging element;wherein the charging occurs while maintaining the first wirelesscharging element within the charging range of the floating unit, despitemovements of the floating unit.
 2. The method according to claim 1comprising: detecting, during the positioning and by at least one of thefloating unit and the pool cleaning robot, a spatial relationshipbetween the pool cleaning robot and the floating unit; and wherein thepositioning is responsive to the spatial relationship.
 3. The methodaccording to claim 2 wherein the positioning comprises instructing thepool cleaning robot to move based on the spatial relationship.
 4. Themethod according to claim 2 wherein the positioning comprises moving thefloating unit based on the spatial relationship.
 5. The method accordingto claim 1 wherein the positioning comprises moving the floating unit toa predefined area that is known to the pool cleaning robot.
 6. Themethod according to claim 1 comprising sensing by the floating unit animpact of a wind on the floating unit, and wherein the positioning isresponsive to the impact of the wind.
 7. The method according to claim 1comprising attaching the pool cleaning robot to the floating unit duringa wireless charging period.
 8. The method according to claim 1 whereinthe positioning comprises moving the pool cleaning robot below thefloating unit.
 9. The method according to claim 1 comprisingmechanically coupling the pool cleaning robot to the floating unit, atleast during the wireless charging.
 10. The method according to claim 1comprising magnetically coupling the pool cleaning robot to the floatingunit, at least during the wireless charging.
 11. The method according toclaim 1 wherein the first wireless charging element is positioned at abottom of the pool cleaning robot and wherein the positioning comprisesrotating the pool cleaning robot.
 12. The method according to claim 1wherein the positioning comprises redirecting a movement towards thefloating unit when a current path will lead the pool cleaning robot toreach the floating unit at a position that increases an instability ofthe floating unit.
 13. The method according to claim 1 wherein thepositioning comprises calculating a future position and orientation ofthe floating unit due to floating unit movements selected out ofrolling, pitching and sideways drifting, and directing the pool cleaningrobot towards the future position.
 14. The method according to claim 1comprising delaying a charging of the pool cleaning robot when movementsof the floating unit exceed a threshold.
 15. A pool cleaning system,comprising: a floating unit; and a pool cleaning robot; wherein at leastone of the floating unit and the pool cleaning robot is configured tomove to a position in which a first wireless charging element of thepool cleaning robot is within a charging range of a second wirelesscharging element of the floating unit; wherein the floating unit iselectrically and mechanically coupled to an external power source; andwherein the second wireless charging element is configured to charge thefirst wireless charging element, wherein the charging occurs whilemaintaining the first wireless charging element within the chargingrange of the floating unit, despite movements of the floating unit. 16.The pool cleaning system according to claim 13 wherein one or more ofthe floating unit and the pool cleaning robot is configured to detect,during the positioning, a spatial relationship between the pool cleaningrobot and the floating unit; and wherein the positioning is responsiveto the spatial relationship.
 17. The pool cleaning system according toclaim 13 wherein one or more of the floating unit and the pool cleaningrobot comprises a mechanical coupling element for mechanically couplingthe pool cleaning robot to the floating unit, at least during thewireless charging.
 18. The pool cleaning system according to claim 13wherein one or more of the floating unit and the pool cleaning robotcomprises a magnetic coupling element for magnetically coupling the poolcleaning robot to the floating unit, at least during the wirelesscharging.
 19. The pool cleaning system according to claim 13 wherein thepool cleaning robot is configured to redirect a movement of the poolcleaning robot and reentering a path towards the floating unit when amovement directs the pool cleaning robot to meet the floating unit at anunstable positioning or docking.
 20. A pool cleaning robot thatcomprises: a sensor; a controller; a first wireless charging element;and a drive motor; wherein the sensor is configured to sense a locationof a floating unit that is electrically and mechanically coupled to anexternal power source, wherein the controller is configured to controlthe drive motor, based on a sensed location of the floating unit, to (a)move the pool cleaning robot to a position in which the first wirelesscharging element is within a charging range of a second wirelesscharging element of the floating unit; and (b) to maintain, at leastduring a charging period, the first wireless charging element within thecharging range of the floating unit, despite movements of the floatingunit; and wherein the first wireless charging element is configured tobe charged by the second wireless charging element, during the chargingperiod.